Note that the rst detection at frequency F 3, corresponds to a 0 data bit and the second detection at F 3 corresponds to a 1 data bit.Luca Cazzanti Centre for Maritime Research and Experimentation (CMRE) Julia Hsieh Julia Hsieh This person is not on ResearchGate, or hasnt claimed this research yet.
Sonar Simulation Toolset Sst Software Download Citation CopyG.s. Edelson BAE Systems Download full-text PDF Read full-text Download full-text PDF Read full-text Download citation Copy link Link copied Read full-text Download citation Copy link Link copied Citations (4) References (14) Figures (10) Abstract and Figures Differential frequency hopping (DFH) is a fast frequency hopping, digital signaling technology that achieves the desirable performance features of non-interfering spread spectrum operation, spectral re-use, fading mitigation, and interference resistance. Therefore, DFH coding provides the critical capability for multiple users to seamlessly communicate in the bandwidth-limited acoustic channel. In previous work, DFH coding has been shown to be superior to other coding schemes in additive Gaussian white noise and Rayleigh-fading environments when considering the joint constraints of multiple user access, detectability mitigation, and the presence of jamming. In this paper, we describe the auto-synchronizing single-user DFH decoder we have developed for a single hydrophone receiver. We present the performance of this decoder on multi-user simulated data and on multi-user data collected at sea during the Rescheduled Acoustic Communications Experiment (RACE08).We use the Sonar Simulation Toolset (SST) to produce the simulated data for soft through hard bottom compositions to provide a range of multipath severity to gain insight into DFH performance across environments. ![]() Figures - uploaded by G.s. Edelson Author content All figure content in this area was uploaded by G.s. Edelson Content may be subject to copyright. Sonar Simulation Toolset Sst Software For Free Public FullDiscover the worlds research 20 million members 135 million publications 700k research projects Join for free Public Full-text 1 Content uploaded by G.s. Edelson Author content All content in this area was uploaded by G.s. ![]() Edelson BAE Systems P.O. Box 868 Nashua, NH 03061-0868 USA University of W ashington - Applied Physics Lab Box 355640 Seattle, W A 98105 USA Abstract Differential frequency hopping (DFH) is a fast frequency hopping, digital signaling technology that achieves the desirable performance features of non-interfering spread spectrum operation, spectral re-use, fading mitigation, and inter- ference resistance. Therefor e, DFH coding provides the critical capability for multiple users to seamlessly communicate in the bandwidth-limited acoustic channel. In this paper, we describe the auto-synchronizing single- user DFH decoder we have developed f or a single hydrophone receiver. W e present the performance of this decoder on multi- user simulated data and on multi-user data collected at sea during the Rescheduled Acoustic Communications Experiment (RACE08). W e use the Sonar Simulation T oolset (SST) to produce the simulated data for soft through hard bottom compositions to provide a range of multipath severity to gain insight into DFH performance across envir onments. Based on these initial results, the DFH waveform sho ws considerable promise for computationally minimal, high reliability communications among uncoordinated users in an underwater acoustic channel. I. I NTR ODUCTION Differential frequency hopping (DFH) is a frequency hop- ping digital signaling technology that achieves the desirable performance features of noninterfering spread spectrum oper- ation, spectral reuse, multipath fading mitigation, and interfer- ence resistance 3, 4, 7. For DFH waveforms, the frequency of the transmitted tone depends on both the current data symbol and the previous transmitted tone. That is, given a data symbol X n and the frequency of the previous hop F n 1, the frequency of the next hop is determined as F n G ( F n 1, X n ) where the function G can be viewed as a directed graph that has nodes corresponding to frequencies and vertices labeled with input data. Trellis models, often used in depicting and analyzing conv o- lutional codes, are easily applied to a differential frequency- hopped signal, as shown in Fig. The vertical axis of the trellis corresponds to frequency, while the horizontal axis corresponds to time intervals. ![]() Example DFH trellis for a hop set of size four are M possible states at each stage in the trellis. The branches leaving each state terminate at the frequencies that are possible at the next hop, given the current frequency state. A label on each branch indicates the encoded bits that correspond to the transition from the current transmitted frequency to the next transmitted frequency. A trellis-based DFH receiver can reconstruct transmissions that are missing due to a fading channel or collisions with other users. The trellising also allows for the simultaneous demodulation of multiple users by assigning unique trellises to individual users. For the trellis in Fig. M is 4, and the data sequence shown by the dotted line is 0110.
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